HCA: Hermit Crab Association

Hi & thank you all...been reading and learning for a few weeks.
I have a 40 g. tank with 4 hermit friends (all on the smaller side)
I am using 2 side by side critter containers for their fresh & salt water baths. (each holds about 3 cups) When I fill them both up the humidity is too high in the tank. (I'm in the humid Western NC mountains) So, I fill one up and keep one at 1/3 full. Perfect humidity. **both are deep enough for submersion by all hermits.

MY MAIN QUESTION: If only one pool can be deep...and if only one pool can have a bubbler, which should it be the fresh or salt pool?

My second question: Is it best (in a 40g tank) to have the pools side by side or separated?
(I know using one bubbler splitter requires them to be side by side - but I can't do that anyway due to humidity issues)

Thank you Hermit High-brows!

I'm not sure it matters too much which is deeper as purple pinchers don't usually like to swim. I'd suggest using a bubbler in the fresh though, to cut down on potential salt spray! It takes a lot of salt to be harmful but the buildup can get annoying to clean.